Gold Glass dries out my hands. Optimum does not. I would just try Optimum and see what you think. It seems Optimum has better lubrication. Plus the dilution ration is 1/2 oz Optimum to one gallon water. The stuff is thick as molasses in January. With that being said, I would buy Gold Class anytime too.
I would make a recommendation that could save you money in shampoo when I comes to washing a MC. Buy 3-5 quality wash mitts, I like the style you are using. Try Meguiars white MF wash mitt, awesome ( btw), fill up a 1gal/2gal of water and your desired amount of soap. Take the grit guard out and once you are done with a mitt, put the used mitt in an empty bucket. Like a GD rinseless, but with reg shampoo and rinse. You will save water and save on soap. You don't have to worry about any dirt being reintroduced into your wash bucket, only clean wash mitts ever enter, never to return

This would theoretically work on a car but you would need 10 wash mitts and mor water and soap.
I think a Grit Guard occupies too much water when you compare it to the amount of water/shampoo needed to wash a small MC. Don't get me wrong, I continue to uses Grit Guards with my cars, but if I owned a MC I would not use a grit guard.